1. Field of the Invention
This invention relates to a sliding member which includes a diamond film having a low coefficient of friction and a high degree of wear resistance, while not causing wear to any mating part, and which is particularly suitable for use in a bearing, mechanical seal, etc.
2. Description of the Related Art
Diamond is a very hard substance having a Vickers hardness of 8000 or more. Various attempts have, therefore, been made to coat the surface of a sliding member with diamond to improve its wear resistance. Any ordinary coating method, such as chemical vapor deposition (CVD), can, however, form only a film of diamond having a surface roughness of one micron or more. Diamond is so hard that a film thereof is very difficult to grind until it has a surface roughness not exceeding 0.5 micron. Moreover, if a sliding member has a sliding surface which is not flat, its grinding itself is difficult. The hard and rugged surface of a diamond film on a sliding member not only gives rise to a very high coefficient of friction, but also causes heavy abrasive wear to its mating part, which is likely to render the sliding member unsuitable for use.
If a sliding member having a sliding surface formed by a diamond film is used in a dry mode not involving the use of any lubricating oil, etc., the heat which is generated during sliding at a high temperature causes diamond to change to graphite having a lower degree of hardness, and the sliding surface, therefore, has a lower degree of wear resistance.